The invention relates to an expansible anchor for fastening to a panel-shaped building material. A panel-shaped building material is, for example, a plasterboard panel or a panel made of some other building material. It may also be, for example, the wall of a hollow block or the like. The expansible anchoring according to the invention is also suitable for anchoring in a soft, for example porous, building material, such as aerated concrete.
An expansible anchor of this kind is known from DE 197 20 033 A1. The known expansible anchor has an anchor sleeve having expansion tongues projecting forwards from the anchor sleeve. Furthermore, the known expansible anchor has an expander body in the form of an expander cone which is arranged in front of the expansion tongues. For spreading open the expansion tongues, the expander body is drawn in between the expansion tongues by screwing in an expander screw, the expander body pushing the expansion tongues apart, that is to say spreading them open. The spread-open expansion tongues engage behind the panel-shaped building material and thus anchor the expansible anchor interlockingly against the building material.
The known expansible anchor has the disadvantage that the expander body falls out from between the expansion tongues if the expander screw is unscrewed from the expansible anchor or at the latest, when a fresh attempt is made to screw the expander screw into the expansible anchor, if the expander screw is pressed with a slight axial pressure against the expander body. It may be necessary, or at least desirable, to unscrew the expander screw after the expansible anchor has been anchored, for example for renovation purposes or when an article fastened using the expansible anchor is to be replaced or removed. The known expansible anchor, once anchored, cannot be re-used; its anchor sleeve must be removed after unscrewing from the drilled hole and a fresh expansible anchor used. The expander body remains in the inaccessible cavity on the rear side of the panel-shaped building material.
The invention is based on the problem of developing an expansible anchor of the kind described above so that it can be re-used after a screwed-in expander screw has been unscrewed.
This problem is solved according to the invention. The expansible anchor according to the invention has a locking connection which engages when the expander body is drawn in between the expansion tongues. In the engaged state, the locking connection holds the expander body of the expansible anchor according to the invention in the position of the anchor sleeve in which it is drawn in between the expansion tongues. As a result, after the expander screw has been unscrewed the expander body remains in the position in which it is drawn in between the expansion tongues. Even if the expander screw is subsequently re-inserted into the expansion anchor and an axial pressure exerted on the expander body by the expander screw, the locking connection of the expansible anchor according to the invention holds the expander body in the position in which it is engaged between the expansion tongues. Because the expander body in the position in which it is drawn in between the expansion tongues hold the expansion tongues in a spread-open position, the locking connection has the effect that the expansible anchor according to the invention remains anchored against the building material even when the expander screw is unscrewed. The expansible anchor according to the invention accordingly has the advantage that its expander body cannot be lost when the expander screw is unscrewed after the expansible anchor has been anchored. A further advantage of the expansible anchor according to the invention is that it remains anchored in the building material even after the expander screw has been unscrewed. The locking connection between the expander body and the anchor sleeve an also be effected indirectly by way of the expansion tongues, that is to say that the expander body is locked together with the expansion tongues.
In a variant of the invention the expansible anchor has one or more locking hooks arranged substantially axially parallel, which forms a locking connection together with a locking tongue which is likewise arranged substantially axially parallel. In the engaged state, the locking hook engages over a free end of the locking tongue and thus holds the expander body in the position in which it is drawn in between the expansion tongues. At the same time, the locking hook can be connected to the expander body or the anchor sleeve, while the locking tongue is connected to the respective other of those two components. The looking hook and/or the locking tongue are resilient.
In a development of the invention the expansible anchor has an anti-rotation device which holds or guides the expander body non-rotatably on the anchor sleeve. The anti-rotation device prevents the expander body from co-rotating with the expander screw when the expander screw is screwed into the expansible anchor. The anti-rotation device can have, for example, a lug, rib or the like, which engages between the expansion tongues and thus guides the expander body non-rotatably but axially displaceably on the anchor sleeve. In variants of the invention it is also possible for the locking hook and/or the locking tongue of the locking device to form the anti-rotation device.
In a preferred variant of the invention the expander body and the anchor sleeve are formed integrally with one another, they are connected to one another by way of a predefined breakage point which is broken, for example it tears off, when the expander body is drawn in between the expansion tongues. This variant of the invention enables the expansible anchor according to the invention to be made in one piece and has the further advantage that the expander body is captively connected to the anchor sleeve until the expander screw is screwed in.
In a preferred variant, the expansible anchor according to the invention is produced from plastics, for example by injection-moulding or transfer-moulding. This enables the expansible anchor according to the invention to be manufactured economically. The expander body and the anchor sleeve can especially be produced in one piece from plastics without difficulty and in one operation.